Roles of GDF3 in the differentiation and function of the adipocyte

描述（由申请人提供）：TGF-β超家族信号传导调节体外前脂肪细胞确定和分化。这些分泌的配体在脂肪形成的刺激和抑制中起作用。前体细胞系向脂肪细胞的确定和随后的分化受到骨形态发生蛋白（BMP）2、4和7的刺激。BMP 7诱导的脂肪细胞分化可被另一TGF-β超家族成员GDF 8/肌生长抑制素抑制。TGF-β在体外和体内也对脂肪生成具有拮抗作用。我们推测，GDF 3，另一个TGF-β超家族成员和本提案的主题，也在调节脂肪形成和/或影响成熟脂肪细胞的功能中起重要作用。首先，GDF 3在脂肪组织中表达，并在白色脂肪贮库中响应于高脂肪饮食而显著上调，脂肪细胞和基质血管部分不成比例地增加。其次，通过腺病毒转导在体内过度表达GDF 3导致对高脂肪饮食的脂肪形成作用的更大敏感性，这反映在更大的体重增加、脂肪组织质量、更高的瘦素水平和更大的脂肪细胞大小。相反，我们对Gdf 3-/-小鼠的研究揭示了对饮食诱导的肥胖的保护，包括正常的身体和脂肪组织质量以及脂肪细胞大小，尽管摄入了更大的热量。因此，GDF 3可能在调节脂肪形成和/或成熟脂肪细胞功能中起作用。具体目的1-检查GDF 3对细胞增殖、存活和分化的影响。我们将研究外源性GDF 3蛋白对两种成脂细胞系的增殖、有丝分裂克隆扩增、凋亡和分化的影响。具体目标2-评估GDF 3对成熟脂肪细胞功能的影响。将分析完全分化的3 T3-L1细胞以确定外源性GDF 3蛋白施用是否对脂肪生成、脂解和其他成熟脂肪细胞功能具有影响。具体目标3-定义脂肪细胞中GDF 3信号传导的基本组分，并确定是否与棕色/白色脂肪细胞命运决定有关。我们将进一步确定GDF 3与其受体和其他影响脂肪形成的超家族成员的相互作用。具体目的4-检查体内脂肪组织中GDF 3过表达的后果。我们将产生在药物强力霉素的可逆控制下在脂肪组织中选择性表达GDF 3的转基因小鼠。

DESCRIPTION (provided by applicant): TGF-( superfamily signaling regulates pre-adipocyte determination and differentiation in vitro. These secreted ligands play roles in the stimulation and inhibition of adipogenesis. The determination and subsequent differentiation of precursor cell lines into adipocytes is stimulated by bone morphogenetic proteins (BMPs) 2, 4 and 7. BMP7-induced adipocyte differentiation can be inhibited by GDF8/myostatin, another TGF-( superfamily member. TGF-( is also antagonistic to adipogenesis in vitro and in vivo. We hypothesize that GDF3, another TGF-( superfamily member and the subject of this proposal, also plays an important role in regulating adipogenesis and/or in affecting the function of mature adipocytes. First, GDF3 is expressed in adipose tissues and is significantly up regulated in white adipose depots in response to high fat diets, with disproportionate increases in the adipocyte and stromal vascular fractions. Secondly, over expression of GDF3, in vivo, by adenoviral transduction results in a greater sensitivity to the adipogenic effects of high fat diets, reflected by greater weight gain, adipose tissue mass, higher leptin levels, and greater adipocyte cell size. Conversely, our studies of Gdf3-/- mice have revealed a protection from diet- induced obesity, including normal body and adipose tissue mass and adipocyte cell sizes, despite a greater caloric intake. Therefore, GDF3 may function in to regulate adipogenesis and/or mature adipocyte function. The aims of the application are as follows: Specific aim 1- Examine the effects of GDF3 on cell proliferation, survival, and differentiation. We will examine the effects of exogenous GDF3 protein on the proliferation, mitotic clonal expansion, apoptosis, and differentiation of two adipogenic cell lines. Specific aim 2- Assess GDF3's effects on mature adipocyte function. Fully differentiated 3T3-L1 cells will be analyzed to determine if exogenous GDF3 protein administration has effects on lipogenesis, lipolysis, and other mature adipocyte functions. Specific aim 3- Define the essential components of GDF3 signaling in adipocytes and determine if there is a link to brown/white adipocyte fate decisions. We will further define GDF3's interactions with its receptors and with other superfamily members that affect adipogenesis. Specific aim 4- Examine the consequences of GDF3 over expression in adipose tissues in vivo. We will generate transgenic mice which express GDF3 selectively in adipose tissues under the reversible control of the drug, doxycycline.